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Limit Outgoing Emails and Turn On SMTP Authentication

These two settings help stop spam from your server. This guide needs root access. It is meant for VPS and dedicated server owners using WHM.

Email2 min read18 steps
Note: You need root access. Shared hosting users cannot change these settings. They can ask Hostvento support instead.

What do these settings do?

SMTP is the system that sends email. A limit on outgoing mail caps how many messages one domain can send in an hour. If a hacker takes over an account, the limit stops a flood of spam. SMTP authentication means the server asks for a username and password before it sends mail. Without it, anyone could use your server as a free post office.

Limit emails per hour

  1. Log in to WHM as root.
  2. Type Tweak Settings in the search box and open it.
  3. Open the Mail tab.
  4. Find The maximum each domain can send out per hour. Use the find box on the page to search for "maximum".
  5. Type a number that suits your real needs. A small business may need a low number. Do not choose one that blocks normal use.
  6. Click Save at the bottom.

You can also set the limit for one package in Edit a Package, and for one domain in Edit Mail Delivery Limits if it is available. Names can vary by version.

Mail over the limit is held back, or rejected, until the next hour. Real senders may need to wait.

Require SMTP authentication

  1. Open WHM and search for Exim Configuration Manager.
  2. Click Basic Editor.
  3. Look in the Security area.
  4. Find Require SMTP authentication for outgoing mail. Labels differ between versions, so read nearby options with care.
  5. Switch the option on, if it is offered.
  6. Scroll to the bottom and click Save.

Warning: A wrong change to the mail server can stop mail for every account. Take a backup of the Exim settings first, and test right after you save.

Set up your mail programs

  1. Open your email program.
  2. Open the outgoing server (SMTP) settings.
  3. Tick the option that says the server requires authentication.
  4. Use your full email address and password.

Test

  1. Send a test email from a program with authentication on.
  2. Check that it is delivered.
Tip: Watch your mail queue now and then for strange spikes. A large queue can mean a hacked account.

Quick recap

  • This needs root access in WHM.
  • Set an hourly limit in Tweak Settings, Mail tab.
  • Turn on SMTP authentication in the Exim settings.
  • Back up first, and test after saving.